Preventing Chemical Foodborne Illness

Phillip T. Tybor, William C. Hurst, A. Estes Reynolds & George A Schuler
Extension Food Science

Protecting public health is a critical factor associated with the food supply. Potential hazards that can cause public health problems have three basic forms, biological, physical and chemical.

Chemical hazards refer to four different agents that are sources of potential foodborne illness. The agents are metals, pesticides, intentional food additives and other chemical residues. The residues from these agents, if consumed in a large enough dose, can be harmful to humans.

Although biological hazards pose the greatest potential risk to the food supply, an understanding and knowledge of chemical residues is important for all individuals, whether they are agricultural producers, food processors/handlers or consumers. This publication is intended as a resource for understanding and preventing chemical foodborne illness.

Chemical Foodborne Illness

Chemical foodborne illness is called chemical poisoning. Some of the known chemical agents involved in chemical foodborne illness are beneficial and essential in the diet as nutrients, others serve to preserve food or improve eating quality, while others are beneficial in food production or to assure a clean and sanitary food handling environment.

Examples of beneficial chemicals (Table 1) are some of the metals and vitamins (nutrients), nitrite (a preservative), monosodium glutamate (a flavor enhancer), pesticides (for insect, weed and rodent control) and cleaners (for environmental hygiene). Illness or chemical poisoning occurs when abnormally high levels (dosages) of the beneficial chemicals contaminate food. Other chemicals, as in the case of poisonous plants or animals, are strictly recognized as harmful.

The route of entry for many of the chemicals into the food supply can occur in the home, retail markets, wholesale markets, distribution warehouses, restaurants, transportation systems or food processing plants, on the farm, or the chemicals can be naturally present in the food. Chemical foodborne illness is normally the result of a human error that could have been prevented. The symptoms of each illness and onset time are different among the six basic agents. Knowledge of specific agents, sources, symptoms and onset times is important to better ensure control and prevention. These are discussed in the following sections.

Chemical Hazards, Sources and Control

Metals

The illnesses caused by metals are called metal poisoning. A metal is an inorganic substance also referred to as a mineral. Metals are widespread in nature. Many are found in the soil and are therefore a common and historic component of foods. The metals commonly identified as potential chemical hazards are:

• arsenic
• antimony
• cadmium
• copper
• lead
• tin
• zinc
• mercury

Through the investigation of metal poisoning outbreaks, the source of the illness has been traced primarily to food handling equipment and utensils made of inappropriate materials. When high acid foods (pH less than 4.6) come in contact with the equipment or utensil surface corrosion occurs. Through corrosion, the metal is released onto or in the food as a contaminant and the ultimate source of metal poisoning. High acid foods include citrus fruits, fruit drinks, fruit pie fillings, tomato products, sauerkraut and carbonated beverages.

Chemical poisonings by antimony, cadmium, copper, lead, tin and zinc are traced to sources where corrosion has taken place (Table 2).

The major form of arsenic found in foodstuffs is pentavalent arsenic. The FDA has set an allowable limit of 2.6 parts per million (ppm) for arsenic in food sold into interstate commerce. However, much seafood exceeds these tolerances, measuring as much as 40 to 170 ppm. Fortunately, this form of arsenic has relatively low toxicity, so is a concern only for those persons whose diet is inordinately high in seafood.

Spring waters, which are high in bicarbonate, have been found to contain 0.4 to 1.3 ppm trivalent arse-nic, a more toxic form. The recommended limit for trivalent arsenic in drinking water in the United States is 10 parts per billion (ppb). Thus, any potential drinking water supplies drawn from natural spring wells should be tested for arsenic levels. Arsenic poisoning can occur by ingestion of organo-arsenicals found in some pesticides and herbicides.

In recent years, arsenic has been largely removed and other organic compounds have been substituted in pesticide formulations, thereby decreasing the risk. Nevertheless, agricultural workers using known arsenicals should take proper safety measures. Chronic low-dose exposure to arsenic leads to lung and skin cancer, leukemia and goiter.

Generally, the onset of metal poisoning symptoms is rapid. In several instances, symptoms can begin to occur during food consumption. The digestive disorders of nausea and abdominal pain are associated with the small intestines, the upper gastrointestinal portion of the digestive system.

Mercury poisoning is different from the other forms of metal poisoning. It causes neurological symptoms rather than digestive disorders. The source of mercury poisoning is primarily contamination of food from polluted water containing mercuric compounds from industrial waste or organic mercury contained in some fungicides. Food or feed grains treated with mercury-containing fungicides are a potential source for transmission of the metal through both animal and cereal foods. The onset time is one week or more, at which time the symptoms of numbness, weakness of the legs, spastic paralysis and impaired vision are noted. Blindness and coma are extreme symptoms of the poisoning. Prevention is best accomplished by purchasing foods from reputable sources. Proper environmental disposal of mercuric waste products is important to prevent water contamination and any additive effects on food. Proper use of approved fungicides for food and feed grains will eliminate the potential for carry-over into the food chain.

Pesticides

Pesticides are a group of chemicals that includes insecticides, fungicides, herbicides, bactericides, nematicide, growth regulators, fumigants and fertilizers. Many of these chemicals are used throughout the food supply system. Pesticides are used in agricultural crop production, in food processing facilities, at wholesale and retail distribution points, in restaurants and in the home. These chemicals are intended to kill insects, fungus, weeds, rodents and other pests that reduce the quality of food. Pesticides are known poisons.

The greatest public health risk associated with pesticides is poisoning resulting from large doses absorbed through the skin, ingested orally, or inhaled through normal respiration (breathing). Pesticide poisoning by any of these three routes results in an immediate personal injury.

The principal route of entry in foodborne illness is the oral route, where individuals become sick from eating highly contaminated foods. The contamination can result from numerous sources where accidental or indiscriminate exposure of the food to a pesticide has occurred. Pesticide spills resulting in food contact, indiscriminate spraying of food-handling facilities or equipment, improper storage of pesticides or mistaken identity of the chemical for a food application at excessively high levels, premature harvest of food crops after pesticide application and incomplete washing of fruits and vegetables are all critical sources of pesticide poisoning. These occur at the farm, in transporting the food, in food processing and in the home.

Three specific forms of pesticide poisoning are associated with foodborne illness: organophosphorus poisoning, carbamate poisoning and chlorinated hydrocarbon poisoning. All three forms affect the neurological system a short period of time after exposure.

Organophosphorus poisoning becomes symptomatic a few minutes to a few hours after exposure. Onset time is related to dose and individual susceptibility. The symptoms are nausea, vomiting, stomach cramps, diarrhea, headache, nervousness, blurred vision, chest pain, confusion and twitching. Convulsions and death can occur if treatment is not administered immediately. The treatment for organophosphate poisoning is usually atropine, but immediately contacting a physician is of ultimate importance. Examples of pesticides containing organophosphorus compounds are parathion and diazinon.

Carbamate poisoning is characterized by an onset time of 30 minutes, with symptoms similar to those for organophosphates. Additionally, abnormal salivation and sweating may occur. Lack of treatment will result in death. Pesticide examples of carbonates are aldicarb and sevin.

Chlorinated hydrocarbon poisoning from sources such as chlordane, lindane and methoxychlor causes nausea, vomiting, dizziness, confusion, general discomfort and muscular weakness. The onset time is 30 minutes to six hours. In extreme cases, convulsions can occur without early symptoms, and coma may follow the convulsive condition. Treatment is important.

Protecting against the possibility of pesticide poisoning is governed by simple but important rules:

• Store and secure pesticides away from food products, not in the same cabinet or under the sink
• Maintain the chemical in its original container
• Read and follow the label instructions
• Handle pesticides like poisons
• Avoid indiscriminate application of chemicals
• Use trained and certified personnel for pesticide application

Intentional Food Additives

Food additives are ingredients that are added to foods in a regulated amount for specific purposes. Some additives enhance the eating qualities of flavor, aroma and texture, others enhance nutritional value while others reduce or prevent spoilage or the growth of pathogenic organisms.

Some food additives, when used in excess, can cause health problems in the case of individual sensitivities (Table 3). Monosodium glutamate, when consumed as part of a food at levels of 1.5 to 3.0 grams, can cause "allergic-type" reactions in sensitive individuals. The foodborne illness is sometimes called the "Chinese restaurant syndrome." Cases typically occur when the excessive dose is consumed on an empty stomach and symptoms can occur immediately upon ingestion. The "allergic-type" reaction lasts from two to seven hours, with some cases lasting as long as 24 hours.

Sulfites are known to cause asthma in sensitive individuals. The "allergic-type" reaction primarily affects severe asthmatics, who comprise one to two percent of the asthmatic population. The threshold level varies between individuals, but ranges from three to 130 milligrams of sulfite (SO₂) equivalents. The cause of the reaction is highly sulfited foods and the reaction is considered to be associated with the inhalation of free SO₂ vapors when swallowing. The free form of sulfite rather than the bound form is the chemical source of the reaction. In extreme cases, the foodborne-induced asthma has resulted in death.

For these reasons, the Food and Drug Administration banned the use of sulfites on fresh fruits and vegetables served primarily at salad bars, effective August 1986. In April 1990, this sulfite ban was extended to include fresh-peeled potato products, to ensure public safety. At present, this ban does not include processed potatoes (canned, frozen or dehydrated), but the FDA is considering this action. Consumers, however, should know that sulfite residues are contained in other foods and sensitive asthmatics should read food label declarations. FDA requires that packaged foods containing 10 ppm sulfite or more must declare this on the label ingredient statement. Also, consumers should know that dehydrated fruits and wines, especially red wines, are treated with sulfites to maintain color and shelf life stability.

Nicotinic acid is the vitamin niacin. Foods such as bakery products and baby foods are special dietary products that may be fortified with niacin for balanced nutrition. Errors in the addition of vitamin concentrates for fortification or improper mixing can result in localized high concentrations of the vitamin. A dosage of 100 to 300 mg of niacin is excessive and is the trigger level for the foodborne poisoning. The duration of the illness is short, about one hour, and is without permanent effects.

Vitamin A is important for balanced nutrition. Excessive doses are known to cause hypervitaminosis A. The toxic dose for adults is between 1,000,000 to 3,000,000 International Units (IU). Classical cases of the illness occur in Eskimos after they eat the organ meat (liver) of polar bears or arctic fox. Individuals consuming vitamin supplements should follow the prescribed label directions to prevent an overdose.

Sodium nitrite is the agent required to cure meat. It produces the typical red color and cured meat flavor, and provides antioxidant protection and prevention of botulinum outgrowth in sausages. At high levels (300 mg/kg body weight), nitrite is toxic if consumed, because it binds with the hemoglobin in red blood cells and prevents the transfer of oxygen within the body. The use level is 156 ppm in sausages and 120 ppm in cured meat. Control is through the use of salt to dilute sodium nitrite to a concentration of 6.25 percent nitrite. It is a controlled additive and must be stored in a locked cabinet and weighed and bagged separately before addition to any product.

Other Chemical Residues (Unintentional Food Additives)

Other chemical residues can enter the food supply and cause illness. Detergents, cleaning compounds, drain cleaners, polishes and sanitizers are common chemicals necessary for the maintenance of a sanitary food handling or preparation area. Improper rinsing of detergents and cleaners from food contact surfaces such as equipment, utensils or tables can result in contaminating residues. Polish applied to these food contact surfaces will also result in residues.

Sodium hydroxide poisoning is the most common foodborne illness from these sources. The first symptoms, burning of lips, mouth and throat, begin within a few minutes. Vomiting, abdominal pain and diarrhea are additional signs of the illness. Prevention of contamination and the potential health hazard is best controlled by:

• Properly training personnel on cleaning and sanitizing.
• Reading and following label instructions on cleaning chemicals.
• Storing cleaning chemicals away from food.
• Maintaining cleaning chemicals in the original, properly labeled container.
• Avoiding the use of empty cleaning chemical containers for food storage.

The moving mechanical parts of equipment and machinery need lubrication. Food processing plants require a great deal of machinery to move raw products through the plant. It becomes imperative, then, that lubricants must be relatively safe and correctly used. Since, at times, lubricants do contact food, only lubricants tested and approved for food use may be used. This regulation prevents the accidental introduction of lubricants and greases into the food supply in small amounts from becoming a health problem. When an item such as hexane, an unapproved compound, was introduced into bottled water, the amount of hexane in the product was not concentrated enough to cause a problem, but the economic impact related to the international recall was substantial. Hexane has a distinct "cleaning" odor that made early detection possible.

It should be obvious from the above examples that:

• Only approved food grade lubricants and greases (mineral oil) should be permitted in the processing area.
• Grease and lubricants, along with cleaners, detergents and sanitizers, should be inventoried and kept in a secured area and strictly supervised to aid in preventing potential contamination.

Summary

The prevention of chemical food poisoning is the responsibility of all food handlers within the food supply system. Knowledge of the potential food-borne illnesses, the causes and control measures are the first steps toward food protection. Applying the controls as standard procedure is the best means of ensuring a safe food supply and public health.

References

Gravani, R. B. Food Science Facts. Dairy and Food Sanitation, I(4):174, 1987.

International Association of Milk, Food and Environmental Sanitarians. Procedures to Investigate Foodborne Illness, 4th Ed., Ames, Iowa, 1987.

Taylor, S. L., J. A. Nordlee and J. H. Rupnow, "Food Allergies and Sensitivities," Food Toxicology, Marcel Dekker, Inc., New York, 1989.

Bulletin 1042/November, 1990

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